General mobile app¹ which was originally $1 on Market but v2 (2019) on Play/Apple store and later free, with μpriced in-app service.

¹ Generalized from app developed c. 2011-03 for One Penny Per Mile.

Free to First Class

.dom TLD authentication and peering

Various DNS related functions are available in the left Navigation when you are logged in to this domain space, with substantial free functionality, visit the page for details.

Documentation

Versions in the wild are infrequently updated, The current versions are within the authentication perimeter. (External mock) .

Micro Priced

The following are IMU denominated at low priced or millage( < 1工), e.g.: capitation, consumer SaaS.

tl:dr

tl:dr[AK] apps for the personal task management and personal ecological impact accounting domains have base free versions with in-app purchase of premium services which are typically priced in the 1-10 工 per month or quarter range.

capitation, 2nd Class

AKPERSON periodic or one-time capitation entitlement, made available in-app in otherwise free apps.

See also public gitHub account. NB: Users id'ed by Google, LinkedIn, or capitation (a token transaction).
In general by "Free" I don't mean zero price (cf. Rate Chart and jobbing response card).